> You haven't kept up with Dart in the last 3 or 4 years, have you??

Not lately, but to my shame the changelog I looked at stopped at Dart 2, so I got a poor picture of things. Looks like variance annotations are still “experimental” though, but I take back what I said about Dart standing still.

It's easy to make that mistake if you don't use Dart, I was also shocked as I had played with Dart 1 long ago, and when I "came back" to it many years later, I found a totally changed language.

I would suggest having a look at the changes since Dart 2 here (Dart is currently at version 3): https://dart.dev/guides/whats-new

There's A LOT of new stuff (new releases every 6 months or something like that, similar to Java).